HDDs are common information storage devices. With improvements in recording density of magnetic HDDs, there has been a demand for improving the performance of magnetic heads and magnetic recording media. In a magnetic hard disk drive, a magnetic head is mounted on a slider that flies above the surface of a magnetic recording medium.
Recently, a technology so-called thermal assisted magnetic recording has been proposed, and a thermal assisted magnetic head also has been put to use. The technology uses a magnetic recording medium having high coercivity. When writing data, a write magnetic field and heat are applied almost simultaneously to the area of the magnetic recording medium where to write data, so that the area rises in temperature and drops in coercivity for data writing. The area where data is written subsequently falls in temperature and rises in coercivity to increase the thermal stability of magnetization.
Commonly, the heat source comes from the thermal assisted magnetic head. FIG. 1a shows a perspective view of a conventional thermal assisted magnetic head 100. The thermal assisted magnetic head 100 includes a slider substrate 110 having an air bearing surface (ABS) (not shown, under) processed so as to provide an appropriate flying height and a laser diode module 130 mounted on the slider substrate 110. The slider substrate 110 includes a bottom surface 112 opposite the ABS, a trailing edge 113 where read and write elements 115 are embedded, and a leading edge (not shown, back) opposite the trailing edge 113. The laser diode module 130 is mounted on the position where the write elements are embedded via a bonding layer. The laser diode module 130 includes a laser diode 131 located near the write element and a mounting base 132 for supporting the laser diode 131. The mounting base 132 is bonded to the slider substrate 110 by using a solder layer, for example. The laser diode 131 emits a laser light to a portion of the magnetic recording medium, which reduces the medium's coercivity. After that, writing is performed by applying write magnetic field to the heated portion; therefore the writing operation is facilitated.
With this arrangement of the laser diode module 130, the laser diode module 130 is vertically mounted on the slider substrate 110, the laser light is emitted perpendicular to top and bottom surfaces of the laser diode 131. As shown, the laser lights with two directions includes a downward laser light 191 emitted from the top surface of the laser diode 131 to the write element (the direction facing to a rotating disk is so-called downward, herein), and an upward laser light 192 emitted from the bottom surface of the laser diode 131 (the direction against a rotating disk is so-called upward), so as to reach a photodiode 133 embedded in the mounting base 132 thereby detecting the laser light.
However, in the HSA level, the upward laser light 192 becomes an undesired light for adjacent laser diode which may affect the stability of the interfered laser diode. Many HGAs with a thermal assisted magnetic head are stacked in a HSA, every two thermal assisted magnetic heads and every two HGAs facing the same rotating disks are so-called a thermal assisted magnetic head pair, a HGA pair, here. FIG. 1b is a partial side view of a HSA 140 that shows two HGA pairs, FIG. 1c is a partial view of FIG. 1b, which shows light interference and coupling status. As shown, a first laser diode 131 of a first thermal assisted magnetic head 100 facing the first disk 180 emits a first upward laser light 192, and a second laser diode 131′ of a second thermal assisted magnetic head 100′ facing the second disk 180′ in the adjacent HGA emits a second upward laser light 192′. Some of the first upward laser light 192 and the second upward laser light 192′ are received and detected by their separated photodiodes 133, 133′ respectively, and some of them are interfered and coupled each other, which may generate negative effect. For example, the first upward laser light 192 may be received and detected by the photodiode 133′ of the second thermal assisted magnetic head 100′, which causes the detection result of the photodiode 133′ is incorrect, and in turns, the laser power of the second thermal assisted magnetic head 100′ could not be controlled well, finally thermal stability of the second thermal assisted magnetic head 100′ is reduced. And the thermal stability of the first thermal assisted magnetic head 100 is weakened vice versa.
Accordingly, it is desired to provide improved HSA with light shielding structure, and disk drive unit to overcome the above-mentioned drawbacks.